Field
Embodiments of the invention relate to designs of a photonic integrated circuit that is capable of suppressing undesirable reflections.
Background
Photonic integrated circuits are used for a wide variety of applications ranging from telecommunications to imaging. These circuits are often designed to have at least some portions that are bi-directional, where light can propagate in a forward and backward direction, sometimes within the same waveguide. This can lead to reflections that may cause undesirable effects, such as interference with other signals.
A few potential solutions have been implemented in an effort to reduce the undesirable reflections. These include tilting the facets of waveguides relative to the direction of light propagation to help reduce reflections at the air-facet interface, and applying an anti-reflective coating upon facets and other surfaces where reflections are undesirable. Such techniques may reduce the reflected radiation amplitude by as much as −40 dB. However, this level of suppression may not be enough, especially when dealing with large dynamic range detection, heterodyne mixing and/or weak input signals to be detected. Such situations are found, for example, in low-coherence interferometry setups, including optical coherence tomography (OCT) systems.